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Why You Need Sugar to Exercise Intensely

All knowledgeable athletes in endurance sports eventually learn that they need to take sugar during competitions lasting more than an hour to be able to compete effectively. Muscles use sugar, fat and, to a lesser degree, protein for fuel during exercise. The limiting factor to how fast you can move your muscles is the time it takes to get oxygen into the muscles. Since sugar supplies 15 percent more energy for the same amount of oxygen than fat does, you go faster when you take in extra sugar.

Mice who live in the Andean mountains, at an altitude of 4,000 meters, breathe air that has 40 percent less oxygen than the air at sea level. Their muscles use a much higher percentage of sugar than animals that live at sea level (Current Biology. December, 2012). Even their heart muscles need less oxygen than animals at sea level.

Since you are not genetically similar to mice that have breathed oxygen-rare air for centuries, you need to take sugar when you cycle, run, swim, or ski in competitions lasting more than an hour.


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How Sugared Drinks and Sugar-added Foods Lead to Diabetes

When you are not exercising, try to reduce your intake of all soft drinks, table sugar and sugar-added foods because they are FULL OF FRUCTOSE, a type of sugar that appears to increase your risk for becoming diabetic. Fructose in drinks and foods causes a high rise in blood levels of the chemicals that rise in the same manner in people as they develop the metabolic syndrome that precedes the onset of diabetes (Nutrition Metabolism, December 2012;9(68)). Another sugar, glucose, does not cause these blood changes.

More than 35 percent of North Americans become diabetic. Most of these people first develop a condition called metabolic syndrome, characterized by:

• reduced ability to respond to insulin,
• storing fat primarily in your belly,
• having small hips,
• being overweight,
• having high blood triglycerides (>150),
• having low blood HDL cholesterol (<40), • having a fatty liver, • having a fasting blood sugar >100 (HbA1c> 5.7),
• having high insulin levels, and
• having high blood pressure.

The incidence of obesity, diabetes and metabolic syndrome has increased markedly in the last 35 years. At the same time period, there has been a 20 percent increase in the consumption of added sugars and sweeteners in North America.

THE RESEARCH: Overweight men and women, ages 40-72, drank glucose- or fructose-sweetened beverages providing 25 percent of their energy requirements. Blood levels of uric acid, Retinol Binding Protein-4 (RBP-4)and Gamma-glutamyl Transferase (GGT) rose markedly after 10 weeks in those taking fructose-sweetened drinks, but only uric acid levels rose in those taking an equivalent amount of glucose in their drinks. However, uric acid levels rose much higher in those taking fructose drinks.

• High levels of Uric acid are associated with a fatty liver that precedes diabetes.
• Increased blood RBP-4 is associated with inability to respond to insulin and increased fat storage in the belly.
• Elevated GGT shows that the liver may be damaged by a fatty liver.

HOW THE BODY USES CARBOHYDRATES: All carbohydrates are made up of sugars in singles, double, and chains of sugars. Before any carbohydrate can be absorbed from the intestines into the bloodstream, it must first be broken down into single sugars. Not even double sugars can be absorbed.

Of all the known sugars, only four can be absorbed into the bloodstream. Only glucose is allowed to circulate in the bloodstream. The other three are trapped in the liver and must be converted to glucose before they can circulate in the bloodstream.

THE DIFFERENCE BETWEEN GLUCOSE AND FRUCTOSE: Once in the liver, fructose can be used for energy or converted to a sugar storage form called glycogen. When you take in large amounts of fructose, it is converted to a fat called triglyceride. Small amounts of triglycerides are fine because they are a great source of energy for your body. However, large amounts of triglycerides plug up everything in your body.

• They fill cells to block insulin receptors on the cells' outer surface so sugar cannot get into that cell. Then blood sugar levels rise too high and you develop diabetes.
• They fill up your belly to cause abdominal obes

ity which prevents cells from responding to insulin. High blood sugar levels cause sugar to stick to the outer surface membranes of cells to destroy every cell in your body. That's why diabetics suffer heart attacks, strokes, blindness, deafness, dementia and impotence, and can lose virtually every useful bodily function.

WHY FRUIT DOES NOT CAUSE DIABETES: Fruit contains both fructose and glucose, but unlike sugared drinks, fruit has not been shown to increase diabetes risk. Fruit also contains a type of carbohydrate called fiber. When sugars are bound up with fiber, as in fruit, they do not cause as high a rise in blood sugar as foods without fiber.

When food enters your stomach, the pyloric sphincter muscle located at the end on the stomach closes and allows only a liquid soup to pass into the intestines. So an orange can stay in your stomach up to five hours before the fiber passes into the intestines. However orange juice, sugared drinks, and sugar-added food without lots of fiber pass rapidly into the intestines to cause a high rise in blood sugar, followed by a high rise in blood triglycerides that set you up for becoming diabetic.

THE LAST WORD: Restrict all sugared drinks including fruit juices, and all foods with added sugars, except during vigorous exercise.


Another Reason to Eat Plenty of Fruits and Vegetables

The more fruits and vegetables a man eats, the less likely he is to have the type of prostate cancer that kills (Prostate Cancer, published online December 2012).

More than 90 percent of men with prostate cancer have a relatively benign disease that is unlikely to kill them. The average life span for men after they are diagnosed with prostate cancer, treated or untreated, is greater than 23 years. On the other hand, fewer than five percent of prostate cancers are rapidly progressive and can kill. Men who eat large amounts of fruits and vegetables are 40 percent less likely to have this aggressive form of prostate cancer.


This week's medical history:
Arthur Conan Doyle: The Power of Observation

For a complete list of my medical history biographies go to Histories and Mysteries


Recipe of the Week:

Spaghetti Squash Soup

You'll find lots of recipes and helpful tips in The Good Food Book
- it's FREE


December 16th, 2012
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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